Lithium-rich manganese-based lithium ion battery and electrolyte thereof

Abstract

The invention belongs to the field of lithium ion batteries, and particularly relates to a lithium-rich manganese-based lithium ion battery and an electrolyte thereof, the electrolyte is a solution containing a composite solvent and a composite lithium salt, the composite solvent comprises EMC, DEC, FEC and a formula 1 # imgabs 0 #, and the composite lithium salt comprises LiPF6 and a formula 2 # imgabs 1 # lithium salt. Innovative research shows that by adopting the quaternary combined composite solvent to be matched with the special combined composite lithium salt, synergism can be accidentally realized, the physicochemical characteristics of the lithium-rich manganese-based battery can be adapted, oxygen free radicals can be effectively removed, and HF can be effectively captured. Research shows that the electrolyte can effectively improve the long cycle stability of the lithium-rich manganese-based battery at high voltage and high temperature.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery electrolytes, and in particular relates to the field of electrolytes for lithium-rich batteries. Background Art

[0002] In recent years, with the surge in demand for high-energy-density energy storage, lithium-rich manganese-based cathode materials (Li-rich Layered Oxides, LLOs) are regarded as one of the core technologies for the next generation of lithium-ion batteries due to their high specific capacity (>250mAh / g) and low cost. However, LLOs are prone to lattice oxygen release during cycling, triggering irreversible structural phase transitions (such as layered to spinel / rock salt phase transitions) and accompanied by a large number of nucleophilic oxygen radicals (such as O - 、O2 - ) are generated. These active oxygen species not only accelerate the mechanical pulverization of the cathode material and the oxidative decomposition of the electrolyte, but also trigger the dissolution of transition metal ions, leading to battery capacity decay and a surge in interfacial impedance. At the same time, the thermal decomposition of trace water or lithium salts (such as LiPF6) in the electrolyte will continuously produce hydrofluoric acid (HF), which reacts corrosively with the cathode surface, destroying the stability of the electrode / electrolyte interface and further exacerbating the dissolution of transition metals, forming a vicious cycle.

[0003] The rational design of the electrolyte is the simplest, most economical and most promising way to improve the interfacial stability of the negative and positive electrodes. Traditional electrolyte optimization strategies mostly focus on single functional improvements: for example, introducing free radical quenchers (such as anisole derivatives) to neutralize oxygen-active species, or using HF scavengers (such as boron / aluminum compounds) to inhibit acid corrosion effects. However, the above schemes are difficult to synergistically address the problem of multi-interface coupling failure in LLOs systems. On the one hand, conventional quenchers have insufficient selectivity for highly reactive oxygen radicals, and their own oxidation byproducts may aggravate the decomposition of the electrolyte; on the other hand, static HF scavengers are easily ineffective due to dynamic consumption, and it is difficult to maintain sufficient acid neutralization capacity in long-term cycles. In addition, the superposition of single-functional additives may introduce component compatibility risks, leading to problems such as increased electrolyte viscosity and decreased ionic conductivity.

[0004] The existing technology also provides many modified electrolyte solutions. For example, the Chinese patent document with publication number CN119481270A discloses a method based on the high-voltage characteristics of lithium-rich cathode, screening a high-pressure solvent system, and introducing a multifunctional film-forming additive to synergistically construct an organic-inorganic balanced composite interface film (SEI / CEI). By regulating the inorganic phase (such as LiF, LiBO x) and the organic phase (such as containing S / P polymer) ratio, inhibiting the decomposition of the high-voltage electrolyte. The Chinese patent document with publication number CN117996202A proposes a multifunctional composite electrolyte system based on the design of a mixed system of lithium difluorooxalatoborate (LiDFOB) and a phosphate / fluorinated solvent, which effectively improves the electrochemical cycle process of lithium-rich manganese-based positive electrode lithium batteries in room temperature and high temperature environments, and realizes the non-flammable characteristics of lithium-rich manganese-based positive electrode lithium batteries. The Chinese patent document with publication number CN117638233A discloses a high-voltage electrolyte for lithium-rich manganese-based lithium-ion batteries containing fluoroethylene carbonate, which effectively improves the high-voltage performance of the battery, and the electrolyte has good compatibility with the lithium-rich manganese-based positive electrode and shows good performance.

[0005] In summary, existing electrolytes can greatly improve the performance of lithium-rich manganese-based batteries through various strategies, but it is still difficult to simultaneously remove nucleophilic oxygen free radicals and capture hydrofluoric acid. Summary of the Invention

[0006] In response to the problems existing in the prior art, the first purpose of the present invention is to provide an electrolyte for a lithium-rich manganese-based lithium-ion battery, aiming to provide an electrolyte that can adapt to the application requirements of lithium-rich manganese-based batteries and can effectively regulate oxygen free radicals and capture hydrofluoric acid.

[0007] The second object of the present invention is to provide the use of the electrolyte for preparing lithium-rich manganese-based batteries and the resulting batteries.

[0008] Different cathode materials have different physicochemical characteristics and face different problems during application. For example, lithium-rich manganese-based materials face the dual challenges of electrolyte decomposition caused by nucleophilic oxygen free radicals and cathode structure damage caused by HF. This problem is particularly evident at high voltage, high temperature, and during long cycles. To address the problems faced by lithium-rich manganese-based materials, the present invention aims to provide an electrolyte that can adapt to their physicochemical characteristics, can simultaneously scavenge nucleophilic oxygen free radicals and capture hydrofluoric acid, specifically:

[0009] The electrolyte of the lithium-rich manganese-based lithium-ion battery is a solution containing a composite solvent and a composite lithium salt, wherein the composite solvent includes EMC, DEC, FEC and formula 1; the composite lithium salt includes LiPF6 and a lithium salt of formula 2;

[0010]

[0011] The innovative research of the present invention demonstrates that the use of the quaternary composite solvent in combination with the special composite lithium salt achieves unexpected synergy, adapting to the physicochemical characteristics of lithium-rich manganese-based batteries, effectively scavenging oxygen free radicals and capturing HF. Research has shown that the electrolyte of the present invention can effectively improve the long-term cycling stability of lithium-rich manganese-based batteries at high voltages and high temperatures.

[0012] In the present invention, the combination of the quaternary components in the organic solvent is one of the keys to synergistically improving the adaptability of the electrolyte to the physicochemical characteristics of lithium-rich manganese-based batteries and improving their long-cycle stability under high voltage and high temperature. Studies have also shown that further optimizing and controlling the proportions of the components can help further enhance the synergy of the components.

[0013] Preferably, the volume ratio of EMC, DEC, FEC, and Formula 1 in the composite solvent is 3-6:2-6:1-2:1, preferably 4-5.5:2.5-4:1-2:1; and more preferably 5:3:1:1. Studies have shown that the preferred quaternary composite solvent, combined with the control of the aforementioned ratio, can further synergize with the composite lithium salt, helping to further address the problems faced by lithium-rich manganese-based materials such as oxygen free radicals and difficulty in capturing HF, thereby achieving better high-pressure, high-temperature, and long-cycle performance.

[0014] In the present invention, the combination of LiPF6 and lithium salt of formula 2 is another key to synergistically improving the adaptability of the electrolyte to the physicochemical characteristics of lithium-rich manganese-based batteries and improving their long-cycle stability under high voltage and high temperature.

[0015] Preferably, the molar ratio of LiPF6 to the lithium salt of formula 2 is 1:0.05 to 0.5; further, it can be 1:0.07 to 0.3.

[0016] In the electrolyte of the present invention, the molar concentration of the composite lithium salt is 1 to 5M; further, it can be 1.2 to 2M; further, it can be 1.3 to 1.7M.

[0017] The present invention also provides an application of the electrolyte, which is used as an electrolyte to prepare a lithium-rich manganese-based lithium ion battery.

[0018] The present invention also provides a lithium-rich manganese-based lithium ion battery, comprising the electrolyte of the present invention.

[0019] In the present invention, the lithium-rich manganese-based lithium-ion battery refers to a battery whose positive electrode active material is a lithium-rich manganese-based active material.

[0020] In the present invention, the chemical formula of the lithium-rich manganese-based active material is: The chemical formula of the lithium-rich manganese-based active material is: Li x Mn y M zO2, wherein M comprises Ni and / or Co; wherein 1 <x≤1.5;0.4≤y≤0.8;0<z<0.4;

[0021] Preferably, the x is 1.1 to 1.3; the molar ratio of y / z is 1 to 3:1, and y+z is 0.7 to 0.9;

[0022] Furthermore, the lithium-rich manganese-based active material is Li 1.2 Ni 0.267 Mn 0.533 O2.

[0023] In the present invention, the negative electrode of the lithium-rich manganese-based lithium-ion battery is at least one of metallic lithium, carbon material, silicon material, and silicon-carbon material.

[0024] Beneficial effects:

[0025] The present invention adopts the composite solvent of the quaternary combination in combination with the composite lithium salt of the special combination, which can unexpectedly achieve synergy, adapt to the physical and chemical characteristics of lithium-rich manganese-based batteries, and can remove nucleophilic oxygen free radicals (such as O - 、O2 - ), thereby reducing oxidative decomposition of the electrolyte and structural collapse of the cathode material; it can also dynamically capture hydrofluoric acid, improving the stability of the cathode / electrolyte interface. Furthermore, it can assist in the desolvation of lithium ions and preferentially reduce them on the lithium metal anode side to form a lithium fluoride-rich SEI, reducing the growth of lithium dendrites while regulating lithium ion deposition, further improving battery performance. For example, it can achieve excellent high-voltage lithium-rich battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Long cycle data of a button cell with lithium metal matched with a lithium-rich manganese-based positive electrode at 30°C and 4.65V in the electrolyte of Example 1.

[0027] Figure 2 The charge and discharge curve data of the button cell with lithium metal and lithium-rich manganese-based positive electrode matched at 30°C and 4.65V of the electrolyte in Example 1.

[0028] Figure 3 The rate cycling data of the button cell with lithium metal and lithium-rich manganese-based positive electrode matched with the electrolyte in Example 1 at 30°C and 4.65V.

[0029] Figure 4 Example 1: Long cycle data of a button cell with lithium metal and a lithium-rich manganese-based positive electrode matched with the electrolyte at 60°C and 4.65V.

[0030] Figure 5Example 1: Long cycle data of a button cell with lithium metal and a lithium-rich manganese-based positive electrode matched with the electrolyte at 30°C and 4.8V. DETAILED DESCRIPTION

[0031] In the following cases, the formula 1 is represented by the following compounds:

[0032] In the present invention, a quaternary solvent comprising Formula 1 is used in combination with a composite lithium salt comprising LiPF6 and a lithium salt of Formula 2. This can achieve synergy, improve the adaptability of the electrolyte to enhance the lithium-rich manganese-based battery, and solve the problems it faces. The present invention's research also shows that replacing Formula 1 with Comparative Formula A or Comparative Formula B, and replacing Formula 2 with Comparative Formula C or Comparative Formula D, will affect the synergy of the components and are not conducive to solving the control of oxygen free radicals and HF in lithium-rich manganese-based materials.

[0033]

[0034]

[0035] Example 1

[0036] An electrolyte solution was prepared by mixing ethyl methyl carbonate (EMC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and Formula 1 (Formula 1 in this case) in a mass ratio of 5:3:1:1 in a dry argon atmosphere glove box to obtain an organic solvent.

[0037] Then, lithium salt is added, which comprises LiPF6 and Formula 2 in a molar ratio of 1:0.077, dissolved and thoroughly stirred, and after clarification, additives are added and stirred evenly to obtain an electrolyte. The total molar concentration of lithium salt in the electrolyte is 1.4 mol / L.

[0038] The composite electrolyte was injected into a CR2016 button cell. The positive electrode of the button cell used a lithium-rich manganese-based positive electrode (as an optional solution, it includes an active material (lithium-rich manganese-based material), a binder and a conductive agent in a weight ratio of 9:0.5:0.5, wherein the lithium-rich manganese-based active material is optionally Li 1.2 Ni 0.267 Mn 0.533 O2, the binder may be PVDF, and the conductive agent may be acetylene black. A lithium metal anode is used as the negative electrode, and a Celgard 2500 separator is used as the separator. The preparation of the composite electrolyte and the assembly of the button cell are both carried out in an argon-filled glove box, with oxygen and moisture contents below 0.5 ppm (parts per million).

[0039] The lithium-rich manganese-based high-temperature, high-pressure, long-life electrolyte based on oxygen activity regulation and HF dynamic removal obtained in this embodiment and its performance test are shown in the figure:

[0040] Test 1:

[0041] Figure 1 The 1C long cycle data of 800 cycles of button cells with lithium metal and lithium-rich manganese-based positive electrodes at 30°C and 4.65V for lithium-rich battery electrolytes proves the ability of lithium-rich manganese-based high-temperature, high-pressure, long-life electrolytes based on oxygen activity regulation and HF dynamic removal to operate for a long time at high voltage.

[0042] Test 2:

[0043] Figure 2 The 1C charge-discharge curve of a button cell with lithium metal and a lithium-rich manganese-based positive electrode matched at 30°C and 4.65V for the lithium-rich manganese-based high-temperature, high-pressure, long-life electrolyte based on oxygen activity regulation and HF dynamic removal in Example 1 demonstrates the ability of the lithium-rich battery electrolyte to operate for a long time at high voltage.

[0044] Test 3:

[0045] Figure 3 The data are the rate cycling data of the button cell with lithium metal matched with lithium-rich manganese-based positive electrode at 30°C and 4.65V for the lithium-rich manganese-based high-temperature, high-pressure, long-life electrolyte based on oxygen activity regulation and HF dynamic removal in Example 1, which proves the feasibility of rapid charging and discharging of lithium-rich battery electrolytes at large currents.

[0046] Test 4:

[0047] Figure 4 The long cycle data of the button cell with lithium metal matched with lithium-rich manganese-based positive electrode at 60°C and 4.65V for the lithium-rich manganese-based high-temperature, high-pressure, long-life electrolyte based on oxygen activity regulation and HF dynamic removal in Example 1 proves the feasibility of the lithium-rich battery electrolyte under high temperature test conditions.

[0048] Test 5:

[0049] Figure 5 The long cycle data of the button cell with lithium metal matched with lithium-rich manganese-based positive electrode at 30°C and 4.8V for the lithium-rich manganese-based high-temperature, high-pressure, long-life electrolyte based on oxygen activity regulation and HF dynamic removal in Example 1 proves the feasibility of stable circulation of lithium-rich battery electrolyte at high voltage.

[0050] Example 2

[0051] Compared with Example 1, the only difference is that the ratio of the organic solvent is changed. The experimental groups are:

[0052] Group A: In an organic solvent, the weight ratio of EMC, DEC, FEC, and Formula 1 is 4:4:1:1. Other operations and parameters are the same as those in Example 1.

[0053] Group B: In an organic solvent, the weight ratio of EMC, DEC, FEC, and Formula 1 is 3:5:1:1. Other operations and parameters are the same as those in Example 1.

[0054] Group C: The molar ratio of LiPF6 in the composite lithium salt to Formula 2 is 1:0.3; the molar concentration of the total lithium salt in the electrolyte is 1.6 mol / L; other operations and parameters are the same as in Example 1.

[0055] The results of each group are shown in Table 1:

[0056] Table 1

[0057]

[0058]

[0059] It can be seen from Examples 1 and 2 that by adopting the process described in the present invention, excellent high voltage, high temperature and fast charging stability can be obtained.

[0060] Comparative Example 1:

[0061] Compared with Example 1, the only difference is that the composition of the organic solvent is changed. The experimental groups are:

[0062] Group A: Formula 1 in the organic solvent was replaced with an equal volume of comparative formula A;

[0063] Group B: Formula 1 in the organic solvent was replaced with an equal volume of comparative formula B;

[0064] Group C: The organic solvent lacks the fluorocarbonate; the other ingredients, proportions, and other conditions are the same as those in Example 1;

[0065] Group D: Formula 1 was not added to the organic solvent, and the other ingredients, proportions, and other conditions were the same as those in Example 1;

[0066] Group E: In organic solvents, Replace the organic solvent with an equal volume of Formula 1;

[0067] The ratios of other ingredients and the amount of total organic solvent used were the same, and other operations and parameters were the same as in Example 1. The results are shown in Table 2:

[0068] Table 2

[0069]

[0070] It can be seen from Example 1 and Comparative Example 1 that the composite solvent added with the component of Formula 1 described in the present invention can unexpectedly achieve synergy, enhance the adaptability of the electrolyte to the lithium-rich manganese-based material, and obtain high voltage, high temperature and high rate stability.

[0071] Comparative Example 2

[0072] Compared with Example 1, the only difference is that the type of lithium salt component is changed. The experimental groups are:

[0073] Group A: Formula C was used to replace Formula 2 in the composite lithium salt in equal moles;

[0074] Group B: Formula D was used to replace Formula 2 in the composite lithium salt in equal moles;

[0075] Group C: lithium salt, lacking formula 2, and the total lithium salt concentration is the same as in Example 1;

[0076] Other operations, parameters and tests are the same as in Example 1. The results are shown in Table 3:

[0077] Table 3

[0078]

[0079] It can be seen from Example 1 and Comparative Example 2 that the composite lithium salt with the component of Formula 2 added as described in the present invention can unexpectedly achieve synergy, enhance the adaptability of the electrolyte to the lithium-rich manganese-based material, and obtain high voltage, high temperature and high rate stability.

[0080] It can be seen from Examples 1 to 2 and Comparative Examples 1 to 2 that the use of the quaternary composite solvent in combination with the special composite lithium salt can unexpectedly achieve synergy, adapt to the physicochemical characteristics of lithium-rich manganese-based batteries, and remove nucleophilic oxygen free radicals (such as O - 、O2 - ), thereby reducing oxidative decomposition of the electrolyte and structural collapse of the cathode material; it can also dynamically capture hydrofluoric acid, improving the stability of the cathode / electrolyte interface. Furthermore, it can assist in the desolvation of lithium ions and preferentially reduce them on the lithium metal anode side to form a lithium fluoride-rich SEI, reducing the growth of lithium dendrites while regulating lithium ion deposition, further improving battery performance. For example, it can achieve excellent high-voltage lithium-rich battery performance.

Claims

1. The electrolyte of a lithium-rich manganese-based lithium-ion battery is a solution comprising a composite solvent and a composite lithium salt, characterized in that: The composite solvent includes EMC, DEC, FEC and formula 1; the composite lithium salt includes LiPF6 and lithium salt of formula 2; 2. The electrolyte according to claim 1, wherein In the composite solvent, the volume ratio of EMC, DEC, FEC and formula 1 is 3-6:2-6:1-2:

1.

3. The electrolyte according to claim 2, wherein In the composite solvent, the volume ratio of EMC, DEC, FEC and Formula 1 is 4-5.5:2.5-4:1-2:1; preferably 5:3:1:

1.

4. The electrolyte according to claim 1, wherein In the composite lithium salt, the molar ratio of LiPF6 to the lithium salt of formula 2 is 1:0.05-0.

5.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The molar concentration of the composite lithium salt is 1 to 5M.

6. Use of the electrolyte according to any one of claims 1 to 5, characterized in that: It is used as an electrolyte to prepare lithium-rich manganese-based lithium-ion batteries.

7. A lithium-rich manganese-based lithium-ion battery, characterized in that: Contains the electrolyte according to any one of claims 1 to 5.

8. The lithium-rich manganese-based lithium-ion battery according to claim 7, characterized in that: The lithium-manganese-rich lithium-ion battery refers to a battery whose positive electrode active material is a lithium-manganese-rich active material.

9. The lithium-rich manganese-based lithium-ion battery according to claim 8, characterized in that: The chemical formula of the lithium-rich manganese-based active material is: Li x Mn y M z O2, wherein M comprises Ni and / or Co; wherein 1 <x≤1.5;0.4≤y≤0.8;0<z<0.4; Preferably, the x is 1.1 to 1.3; the molar ratio of y / z is 1 to 3:1, and y+z is 0.7 to 0.9; Preferably, the lithium-rich manganese-based active material is Li 1.2 Ni 0.267 Mn 0.533 O2.

10. The lithium-rich manganese-based lithium ion battery according to any one of claims 7 to 9, characterized in that: The negative electrode of the lithium-rich manganese-based lithium-ion battery is at least one of metallic lithium, carbon material, silicon material, and silicon-carbon material.

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